you can right click while holding the ore and aiming at a furnace slot, the first ore will go in the slot then keep holding right click and move the mouse around over the other slots, they should all autofill without the need for you to click again

Hmm... unfortunately I wasn't able to reproduce this issue Can you maybe tell me which plaster textures are affected (id)?

I figured it out. It's not the material, it's the animals. When I walk on the stuff it makes the right sound. When my pig does it sounds like metal. I figured out it's the animals because my fox was walking on grass blocks and although I was walking on the same grass blocks our footsteps sounded completely different.

EDIT: It's actually the combination of the animals and certain blocks. So far it seems to be grass blocks and plaster (Black)

you can right click while holding the ore and aiming at a furnace slot, the first ore will go in the slot then keep holding right click and move the mouse around over the other slots, they should all autofill without the need for you to click again

Yes, but it used to do it a lot faster. Putting in the ore used to be as fast as taking it out.

maybe with a new furnace ... tech3 or tech4 furnace.
I could imagine that when we'll get electricity you may build an automated smeltingsystem.
The existing furnace are fine for me. ... improvement with higher tech-level?!
Survival-mode should be a bit like work to gain something (my oppinion)
so i'm not against your suggestion.
I would prefer to keep the furnace how it is now and take your suggestion for higher technology.